lcsim/src/org/lcsim/util/swim

diff -u -r1.16 -r1.17
--- Helix.java	28 Oct 2005 07:57:27 -0000	1.16
+++ Helix.java	28 Oct 2005 19:56:22 -0000	1.17
@@ -20,7 +20,7 @@

  * All quantities in this class are dimensionless. It has no dependencies
  * except for Hep3Vector (which could easily be removed).
  * @author tonyj

- * @version $Id: Helix.java,v 1.16 2005/10/28 07:57:27 jstrube Exp $

+ * @version $Id: Helix.java,v 1.17 2005/10/28 19:56:22 jstrube Exp $

  */
 public class Helix implements Trajectory
 {

@@ -96,7 +96,7 @@

     * <a href=doc-files/fitting/transport.pdf>
     * Paul Avery's excellent text</a> 
     * @param point Point in Space to swim to. 

-    * @return the length Parameter s

+    * @return the length Parameter alpha

     */
    public double getDistanceToPoint(Hep3Vector point) {
        double tanLambda = sinLambda/cosLambda;

@@ -111,29 +111,26 @@

        
        // first, the point needs to be translated into the first period
        Hep3Vector xDiff = VecOp.sub(origin, point);

-       double zPos = abs(xDiff.z());

+       double zPos = xDiff.z();

        int addedQuarterPeriods = 0;
        // these are two mutually exclusive cases and two while loops
        // may not be the best way to express this 

-       while (zPos > abs(radius*tanLambda*Math.PI/2)) {
-           zPos -= abs(radius*tanLambda*Math.PI/2);
-           ++addedQuarterPeriods;
-       }
-       while (zPos < -abs(radius*tanLambda*Math.PI/2)) {
-           zPos += abs(radius*tanLambda*Math.PI/2);

+
+       while (abs(zPos) > abs(radius*tanLambda*Math.PI/2)) {
+           zPos -= signum(zPos)*abs(radius*tanLambda*Math.PI/2);

            ++addedQuarterPeriods;
        }
        // Make sure the helix is in the right quadrant for the atan

-       if (addedQuarterPeriods % 2 != 0)
-           ++addedQuarterPeriods;
-       if (point.z()<origin.z())

+       if (zPos > 0 && addedQuarterPeriods > 0)

            addedQuarterPeriods *= -1;

+       if (addedQuarterPeriods % 2 != 0)
+           addedQuarterPeriods += signum(addedQuarterPeriods);

        xDiff = new BasicHep3Vector(xDiff.x(), xDiff.y(), zPos);
        double factorA1 = pMag - pz*pz/pMag - (VecOp.dot(xDiff, pCrossB))*rho;
        double factorA2 = (VecOp.dot(xDiff, p0) - xDiff.z()*pz)*rho;
 //       System.err.print("addedQuarterPeriods: " + addedQuarterPeriods);
 //       System.err.printf("result:%.3f + %.3f\n", addedQuarterPeriods*(radius/cosLambda*Math.PI/2), Math.atan(factorA2/factorA1) / -rho);

-       return addedQuarterPeriods*abs(radius/cosLambda*Math.PI/2) + signum(radius)*Math.atan(factorA2/factorA1) / -rho;

+       return addedQuarterPeriods*abs(radius/cosLambda*Math.PI/2) + Math.atan(factorA2/factorA1) / -rho;

    }
    
    

@@ -173,16 +170,16 @@

 
    // Returns the "momentum" at the length s from the starting point.
    // This uses the definition in http://www.phys.ufl.edu/~avery/fitting/transport.pdf

-   public Hep3Vector getTangentAtDistance(double s) {

+   public Hep3Vector getTangentAtDistance(double alpha) {

        double r = abs(radius);
 	   double p0x = r*cosPhi;
 	   double p0y = r*sinPhi;
 	   double p0z = r*sinLambda/cosLambda;
 	   double rho = -cosLambda/radius;
 	   

-	   double px = p0x*cos(rho*s) - p0y*sin(rho*s);
-	   double py = p0y*cos(rho*s) + p0x*sin(rho*s);
-	   double pz = p0z*cos(rho*s) + p0z*(1-cos(rho*s));

+	   double px = p0x*cos(rho*alpha) - p0y*sin(rho*alpha);
+	   double py = p0y*cos(rho*alpha) + p0x*sin(rho*alpha);
+	   double pz = p0z*cos(rho*alpha) + p0z*(1-cos(rho*alpha));

 	   return new BasicHep3Vector(px, py, pz);
    }
    

lcsim/src/org/lcsim/util/swim

diff -u -r1.8 -r1.9
--- HelixSwimmer.java	19 Oct 2005 10:32:54 -0000	1.8
+++ HelixSwimmer.java	28 Oct 2005 19:56:22 -0000	1.9
@@ -12,7 +12,7 @@

  * A simple helix smimmer for use in org.lcsim. Uses standard lcsim units
  * Tesla, mm, GeV. This swimmer works for charged and neutral tracks.
  * @author tonyj

- * @version $Id: HelixSwimmer.java,v 1.8 2005/10/19 10:32:54 jstrube Exp $

+ * @version $Id: HelixSwimmer.java,v 1.9 2005/10/28 19:56:22 jstrube Exp $

  */
 public class HelixSwimmer
 {

@@ -33,7 +33,7 @@

     * @param r0 initial position(x0,y0,z0)
     * @param iq charge iq = q/|e| = +1/0/-1
     */

-   public void setTrack(Hep3Vector p, Hep3Vector r0, int iq)

+   public void setTrack(Hep3Vector p, Hep3Vector r0, double iq)

    {
       double temp = p.x()*p.x()+p.y()*p.y();
       double pmom = Math.sqrt(temp + p.z()*p.z());